Control plane architecture for multicast cache-fill

ABSTRACT

A multicast content delivery system can use both multicast and unicast streams to efficiently use available bandwidth to deliver content. Available multicast content can be identified to gateways serving consumption devices, and the gateways can receive requests for unicast content deliver, but honor the requests with multicast group sessions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 61/242,444, entitled “IP Video Service Delivery ReferenceArchitecture,” filed Sep. 15, 2009, and to U.S. Provisional ApplicationSer. No. 61/242,456, entitled “TV Anywhere Architecture,” filed Sep. 15,2009, the contents of which are hereby incorporated by reference asnon-limiting example embodiments.

BACKGROUND

Consumption of video content used to be a rather straightforward affair.Local television broadcasters transmitted signals over the airwaves, andtelevisions with antennas tuned them for display. As advances intechnology came, similar advances in demand came. Community accesstelevision (CATV) expanded the reach of television into more ruralareas, and Internet technology increased the demand for transmission ofdata and other content, in addition to video content. Development of newtypes of consumption devices, such as mobile telephones, mobiletelevisions and personal computers, increased the complexity of anysystem hoping to support those different types of devices. As we becomemore and more connected, our demand for data steadily increases, placingan increased strain on the information delivery infrastructure. Therewill always be an ever-present need for improved data transmissionefficiency, and increased bandwidth.

SUMMARY

The features described herein generally relate to using transmissionbandwidth and increasing its efficiency. In one example embodiment, atermination system can offer both multicast and unicast transmissions toreceiving gateway devices. Unicast transmissions can generally be usedto provide requested content, while multicast transmissions can be usedto carry the more popular content, thereby relieving some of the demandon the unicast bandwidth. A multicast server can identify multipledifferent versions of a particular piece of multimedia content, and cantransmit a multicast list to its gateway devices, announcing theavailable multicast streams.

The multicast lists supported by a particular termination system canvary. It can vary based on geography, anticipated and actual demand forboth the content title itself and its particular versions (which can bedevice specific). The multicast list can be updated, periodically and,in some cases, incrementally, to provide gateways with current listingsof multicast offerings.

The multicast lists can be filtered prior to delivery, so that aparticular gateway is only informed of the multicast streams that may beof interest or use to the gateway. For example, filtering can be basedon devices known to be supported by the gateway, or on use preferencesof the users of the gateway.

The gateway itself can use the multicast list to process requests fromthe various consuming devices it supports. A device may request aunicast delivery of a piece of content, but the gateway can firstconsult the multicast list before determining whether to honor theunicast request. The gateway can determine that the requested offeringis available in a multicast group stream, and instead of establishingthe requested unicast session, the gateway can subscribe to themulticast group, and supply the received content to the consumingdevice. The content can be packaged in the same way that it would had itarrived in a unicast stream, so the consuming device need not even knowits request was not honored as exactly requested.

In some instances, the gateway may determine that a particular versionof requested content is not available for multicast, and suggest a hintto the consuming device that offers an alternative version that happensto be available in a multicast stream. By convincing the consumingdevice to use the multicast version instead, the gateway can avoid theneed for creating an additional unicast stream, further alleviatingbandwidth demand.

The preceding presents a simplified summary in order to provide a basicunderstanding of some aspects of the disclosure. The summary is not anextensive overview of the disclosure. It is neither intended to identifykey or critical elements of the disclosure nor to delineate the scope ofthe disclosure. The summary merely presents some concepts of thedisclosure in a simplified form as a prelude to the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example and not limitedin the accompanying figures in which like reference numerals indicatesimilar elements and in which:

FIG. 1 illustrates an example communication network on which variousfeatures of the disclosure may be implemented.

FIG. 2 illustrates an example hardware architecture that can be used toimplement any of the various features of the disclosure.

FIG. 3 illustrates another view of a communication network on whichvarious features of the disclosure may be implemented.

FIGS. 4-9 illustrate signaling and process flows for handling variousaspects of multicast sessions.

FIG. 10 illustrates an example process for using multicast bandwidth inaccordance with one or more aspects of the disclosure.

FIG. 11 illustrates an example process for handling a content request inaccordance with one or more aspects of the disclosure.

DETAILED DESCRIPTION

In the following description of various illustrative embodiments,reference is made to the accompanying drawings, which form a parthereof, and in which is shown, by way of illustration, variousembodiments in which aspects of the disclosure may be practiced. It isto be understood that other embodiments may be utilized, and structuraland functional modifications may be made, without departing from thescope of the present disclosure.

FIG. 1 illustrates an example information distribution network 100 onwhich many of the various features described herein may be implemented.Network 100 may be any type of information distribution network, such assatellite, telephone, cellular, wireless, etc. One example may be anoptical fiber network, a coaxial cable network or a hybrid fiber/coax(HFC) distribution network. Such networks 100 use a series ofinterconnected communication lines 101 (e.g., coaxial cables, opticalfibers, wireless, etc.) to connect multiple premises 102 (e.g.,businesses, homes, consumer dwellings, etc.) to a central office 103(e.g., a headend, a processing facility, etc.). The central office 103may transmit downstream information signals onto the lines 101, and eachpremises 102 may have a receiver used to receive and process thosesignals.

There may be one line 101 originating from the central office 103, andit may be split a number of times to distribute the signal to variouspremises 102 in the vicinity (which may be many miles) of the centraloffice 103. The lines 101 may include components not illustrated, suchas splitters, filters, amplifiers, etc. to help convey the signalclearly, but in general each split introduces a bit of signaldegradation. Portions of the lines 101 may also be implemented withfiber-optic cable, while other portions may be implemented with coaxialcable, other lines, or wireless communication paths. By running fiberoptic cable along some portions, for example, signal degradation inthose portions may be significantly minimized, allowing a single centraloffice 103 to reach even farther with its network of lines 101 thanbefore.

The various premises 102 may be connected (through wiring and/orwireless connections) to one another, forming a local premises accessnetwork operationally distinct from another local access network. Theconnected homes forming a local premises access network may be locatednear one another, such as neighboring townhomes, individual apartmentsin a downtown highrise, or the like. For example, a local premisesaccess network may include the various premises 102. Another group ofhomes (not shown) may form a separate local premises access network. Thelocal premises access network of the various premises 102 may beidentifiable from the separate local premises access network. A localpremises access network may also be associated with a particulargeographic region (e.g., city, county, geographic area, etc.). In someembodiments, homes connected to a termination system (TS), such as amodem termination system (MTS), may form a local premises accessnetwork.

The central office 103 may include a termination system (TS) 104, suchas a cable modem termination system (CMTS) in an example of an HFC-typenetwork, which may be a computing device configured to managecommunications between devices on the network of lines 101 and backenddevices such as servers 105-107 (to be discussed further below). In theexample of an HFC-type network, the MTS may be as specified in astandard, such as the Data Over Cable Service Interface Specification(DOCSIS) standard, published by Cable Television Laboratories, Inc.(a.k.a. CableLabs), or it may be a similar or modified device instead.The MTS may be configured to place data on one or more downstreamfrequencies to be received by modems at the various premises 102, and toreceive upstream communications from those modems on one or moreupstream frequencies. The central office 103 may also include one ormore network interfaces 108, which can permit the central office 103 tocommunicate with various other external networks 109. These networks 109may include, for example, Internet Protocol (IP) networks Internetdevices, telephone networks, cellular telephone networks, fiber opticnetworks, local wireless networks (e.g., WiMAX), satellite networks, andany other desired network, and the interface 108 may include thecorresponding circuitry needed to communicate on the network 109, and toother devices on the network such as a cellular telephone network andits corresponding cell phones.

As noted above, the central office 103 may include a variety of servers105-107 that may be configured to perform various functions. Forexample, the central office 103 may include a push notification server105. The push notification server 105 may generate push notifications todeliver data and/or commands to the various premises 102 in the network(or more specifically, to the devices in the premises 102 that areconfigured to detect such notifications). The central office 103 mayalso include a content server 106. The content server 106 may be one ormore computing devices that are configured to provide content to usersin the homes. This content may be, for example, video on demand movies,television programs, songs, services, information, text listings, etc.In some embodiments, the content server 106 may include software tovalidate (or initiate the validation of) user identities andentitlements, locate and retrieve (or initiate the locating andretrieval of) requested content, encrypt the content, and initiatedelivery (e.g., streaming, transmitting via a series of contentfragments) of the content to the requesting user and/or device.

The central office 103 may also include one or more application servers107. An application server 107 may be a computing device configured tooffer any desired service, and may run various languages and operatingsystems (e.g., servlets and JSP pages running on Tomcat/MySQL, OSX, BSD,Ubuntu, Redhat, HTML5, JavaScript, AJAX and COMET). For example, anapplication server may be responsible for collecting television programlistings information and generating a data download for electronicprogram guide listings. Another application server may be responsiblefor monitoring user viewing habits and collecting that information foruse in selecting advertisements. Another application server may beresponsible for formatting and inserting advertisements in a videostream and/or content item being transmitted to the premises 102.

An example premises 102 a may include a modem 110 (or another receiverand/or transmitter device suitable for a particular network), which mayinclude transmitters and receivers used to communicate on the lines 101and with the central office 103. The modem 110 may be, for example, acoaxial cable modem (for coaxial cable lines 101), a fiber interfacenode (for fiber optic lines 101), or any other desired modem device. Themodem 110 may be connected to, or be a part of, a gateway interfacedevice 111. The gateway interface device 111 may be a computing devicethat communicates with the modem 110 to allow one or more other devicesin the home to communicate with the central office 103 and other devicesbeyond the central office. The gateway 111 may be a set-top box (STB),digital video recorder (DVR), computer server, or any other desiredcomputing device. The gateway 111 may also include (not shown) localnetwork interfaces to provide communication signals to other devices inthe home (e.g., user devices), such as televisions 112, additional STBs113, personal computers 114, laptop computers 115, wireless devices 116(wireless laptops and netbooks, mobile phones, mobile televisions,personal digital assistants (PDA), etc.), and any other desired devices.Examples of the local network interfaces may include Multimedia OverCoax Alliance (MoCA) interfaces, Ethernet interfaces, universal serialbus (USB) interfaces, wireless interfaces (e.g., IEEE 802.11), Bluetoothinterfaces, and others.

FIG. 2 illustrates general hardware elements that can be used toimplement any of the various computing devices discussed herein. Thecomputing device 200 may include one or more processors 201, which mayexecute instructions of a computer program to perform any of thefeatures described herein. The instructions may be stored in any type ofcomputer-readable medium or memory, to configure the operation of theprocessor 201. For example, instructions may be stored in a read-onlymemory (ROM) 202, random access memory (RAM) 203, removable media 204,such as a Universal Serial Bus (USB) drive, compact disk (CD) or digitalversatile disk (DVD), floppy disk drive, or any other desired electronicstorage medium. Instructions may also be stored in an attached (orinternal) storage 205 (e.g., hard drive, flash, etc.). The computingdevice 200 may include one or more output devices, such as a display 206(or an external television), and may include one or more output devicecontrollers 207, such as a video processor. There may also be one ormore user input devices 208, such as a remote control, keyboard, mouse,touch screen, microphone, etc. The computing device 200 may also includeone or more network interfaces, such as input/output circuits 209 (suchas a network card) to communicate with an external network 210. Thenetwork interface may be a wired interface, wireless interface, or acombination of the two. In some embodiments, the interface 209 mayinclude a modem (e.g., a cable modem), and network 210 may include thecommunication lines 101 discussed above, the external network 109, anin-home network, a provider's wireless, coaxial, fiber, or hybridfiber/coaxial distribution system (e.g., a DOCSIS network), or any otherdesired network.

The FIG. 2 example is an example hardware configuration. Modificationsmay be made to add, remove, combine, divide, etc. components as desired.Additionally, the components illustrated may be implemented using basiccomputing devices and components, and the same components (e.g.,processor 201, storage 202, user interface 205, etc.) may be used toimplement any of the other computing devices and components describedherein. For example, the various components herein may be implementedusing computing devices having components such as a processor executingcomputer-executable instructions stored on a computer-readable medium,as illustrated in FIG. 2.

One or more aspects of the disclosure may be embodied in acomputer-usable data and/or computer-executable instructions, such as inone or more program modules, executed by one or more computers or otherdevices. Generally, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types when executed by a processor ina computer or other data processing device. The computer executableinstructions may be stored on one or more computer readable media suchas a hard disk, optical disk, removable storage media, solid statememory, RAM, etc. As will be appreciated by one of skill in the art, thefunctionality of the program modules may be combined or distributed asdesired in various embodiments. In addition, the functionality may beembodied in whole or in part in firmware or hardware equivalents such asintegrated circuits, field programmable gate arrays (FPGA), and thelike. Particular data structures may be used to more effectivelyimplement one or more aspects of the invention, and such data structuresare contemplated within the scope of computer executable instructionsand computer-usable data described herein.

As discussed above, the central office of an information distribution oraccess network may transmit information downstream to various userdevices. The transmitted information may include content for consumption(e.g., playback, viewing, listening, display, storage, etc.) by a uservia user equipment, such as a gateway interface device (e.g., gatewayinterface device 111 of FIG. 1) and/or other computing device (e.g.,televisions 112, additional STBs 113, personal computers 114, laptopcomputers 115, wireless devices 116 of FIG. 1). To assist in providingthe content to a user, a content provider may implement in theirdistribution network an information distribution management system thatincludes one or more information distribution management devices (e.g.,one or more servers and/or other devices) configured to perform variousprocesses related to managing the providing of content to the userequipment (e.g., user device).

For example, such managing may include requesting, creating and handlingvarious sessions (e.g., user sessions, multicast group sessions, cachefill sessions, quality of service sessions); managing transmission ofthe content (e.g., managing the establishing of transmissions providingunicast content, such as on demand, and linear content, such asmulticast content); monitoring usage data of the distribution network,and/or handling requests and notifications from user equipment. Asanother example, managing may include managing the content discovery,content locating and content delivery processes of the distributionnetwork. In some embodiments, the managing may be implemented using IP(Internet Protocol) and/or HTTP (Hypertext Transfer Protocol) basedprocesses. For example, communication between various devices may beperformed using HTTP and/or IP packets. In one example, a sessionmanager server may locate a streaming server and/or a multicast addressfor a particular content item, and may notify user equipment of thestreaming server and/or multicast address for the particular contentitem using HTTP or IP packets. The user equipment may receive theparticular content item (via, for example, a unicast signal and/or amulticast signal) by receiving HTTP packets that include fragments ofthe content item and metadata identifying the streaming server and/ormulticast address. In some embodiments, communication between devicesmay use only a single protocol (e.g., only HTTP packets or IP packets).Content items may also be transmitted using the single protocol (e.g.,HTTP packets including fragments of content items). Details of theseprocesses, and others, will be discussed in further detail below.

Content discovery processes may include supporting the discovery ofcontent for various content items being provided by or available on adistribution network. For example, content discovery processes maysupport the discovery of content items for multicast, linear, or othertype of transmission. In some embodiments, content discovery and thevarious related processes may use an HTTP-based approach (e.g.,communication is via HTTP and/or IP packets) that includes communicationbetween user equipment, application servers, and other various serversof the network.

Content locating processes may include supporting the setup of varioussessions and managing the resources of the information distributionnetwork. In some embodiments, content locating processes may enforceentitlement procedures and digital rights management (DRM) licenses.Additionally, in some embodiments, content locating and the variousrelated processes may use an HTTP based approach that includescommunication between user equipment, session manager servers, and otherservers in and out of the network.

Content delivery processes may include supporting the streaming of thecontent items from various servers, such as a streaming server of thecentral office. In some embodiments, content delivery processes mayenable user equipment to receive multicast signals (e.g., signalsdirected at a plurality and/or group of user equipment) and/or receiveunicast signals (e.g., signals directed at a specific user device).Additionally, in some embodiments, content streaming and the variousrelated processes may use an HTTP or IP based approach that includescommunication between user equipment, content servers, and other serversof the central office.

FIG. 3 illustrates an example system of components that may beimplemented on the network 100, and which may be used to implementvarious features described herein to supply various content to users.The system may include one or more sources of the content. For example,in the case of video content (e.g., audiovideo content), there may beone or more video on demand (VOD) content encoders 301, each of whichmay include an application server (such as application server 107)configured to store video content such as movies, television shows,video clips, musical videos, etc. The encoders 301 may include encodinghardware and/or software to provide content in a desired format, such asMPEG.

The system may also include one or more linear content encoders 302.Linear content encoders 302 may be similar to VOD content encoders 301,but may further be configured to supply content according to apredetermined schedule, as opposed to on demand. For example, the NBCcontent service may have one or more linear encoders 302 configured tosupply a video stream of NBC scheduled video programming (e.g., thenightly news) at the appropriate time.

The system may include one or more content packagers 303. The contentpackager 303 may be another application server, but configured toreceive content and package it for delivery to users. This packaging mayinclude, for example, reformatting the content (e.g., video resolutionconversion, coder/decoder conversion, audio conversion, compressionaltering, synchronizing, etc.), encrypting the content, and segmentingthe content (e.g., a two-hour movie may be divided into a plurality ofdiscrete time segments for delivery).

The system may include a license server/key manager 304, which may be aserver configured to manage content entitlement. For example, themanager 304 may contain encryption and/or decryption keys, and cansupply those keys to packager 303 for use in encrypting content fordelivery. The manager 304 may also store information identifying users,and the level(s) of service to which the users are entitled, and maymake determinations as to whether a particular user is actually entitledto receive a piece of requested content.

Content delivery network 305 may be any desired type of communicationnetwork, such as network 109. The network 305 may span a largegeographic area, and may be used to disseminate content or make contentaccessible. For example, some content may be supplied to a streamingserver 306. The streaming server 306 may be a server configured toreceive packaged content, and generate a unicast stream of that contentfor delivery to a user.

Another example may be a multicast server 307. Like the streamingserver, multicast server 307 may also be configured to generate a streamof packaged content. However, the multicast server's stream may be amulticast stream, configured to be received by a plurality of recipientusers.

The multicast server 307 may operate at the direction of a multicastcontroller 308, which may in turn communicate with a session manager 309to establish multicast sessions for the delivery of various pieces ofcontent. Session Manager 309 may be configured to manage one or moresessions of the distribution network by interfacing with various devicesin the distribution network and communicating session information withthe various devices. In some embodiments, the sessions that are managedby session manager 309 may include a user session, a multicast groupsession, a cache fill session, and/or a QoS flow session. For example, auser session may be created upon a user device requesting content, andmay include information related to the requested content and theentitlements of the user device. A multicast group session may becreated upon a user device joining a multicast group of a particulargroup of user equipment, and may include information related to themulticast group. A cache fill session may be created upon a user devicerequesting a cache fill of a particular content item being transmitted(e.g., multicast or unicast), and may include information related to theuser device and the particular content item. A QoS flow session may becreated based on the initiation of a transmission to a user device, andmay include information related to the QoS profile being enforced andthe user device. Details of these sessions will be discussed in furtherdetail below.

The servers 306/307 may communicate with a termination system 310 (e.g.,termination system 104) to ultimately deliver the content to a user'spremises, or to a premises gateway 311 that can, in turn, supply contentto various pieces of user equipment, such as a set-top box 312 a,computer 312 b, or any other desired display device piece of userequipment.

Other servers may be used as part of this delivery as well. For example,a quality of service (QoS) configuration manager 313 may be used todetermine quality of service parameters for a given stream. As anotherexample, a location resolution server 314 may contain geographicidentification information for the various servers 306/307, terminationsystem 310, packagers 303, and other components in the system, and maybe configured to determine which device(s) are closest geographically toa requesting user device. Location resolution device 314 may beconfigured to determine location information for a particular userdevice. For example, in some embodiments, location resolution device 314may receive a location request identifying a particular user device,determine geographic information (e.g., latitude and longitude) for theuser device, determine whether the user device is on-network oroff-network, and transmit the information to the session manager 309. Auser device being on-network may include user devices connected viatermination systems (e.g., termination system 310) of the contentprovider. A user device being off-network may include user devices(e.g., user equipment connected via third party distribution networksthat are not under the management or control of the session manager 309and multicast controller 308.

An entitlement resolution server 315 may be configured to validate auser device's entitlement to a particular content item. For example, insome embodiments, entitlement resolution server 315 may receive avalidate entitlement request identifying a content item; determinewhether a user device has a valid entitlement to the content item, basedon user session information, content item information, and locationinformation of the user device; and transmit the information indicatingthe result of the determination to the session manager 309. Entitlementsresolution server 315 may also be configured to validate a user device'slicense to a particular content item. For example, in some arrangements,entitlement resolution server 315 may receive a validate license requestidentifying a content item, determine whether a user device has a validlicense to the content item, based on user session information andcontent item information, and transmit information indicating the resultof the determination to a license resolution server 316.

License resolution server 316 may be configured to distribute licensesand/or distribute decryption and encryption keys. For example, in someembodiments, license resolution server 316 may distribute encryptionkeys to content packager 303 (or to license server/key manager 304. Thelicense resolution server 316 may also receive a license request from auser device; transmit a request to the entitlement resolution server 315to validate the license; and upon receiving an indication that the userdevice has a valid license, and transmit the license and one or moredecryption keys to the user device.

A content server 317 may also be provided. The content server 317 may beone or more computing devices that are configured to resolve requestsfor content. This content may be, for example, video on demand movies,television programs, songs, text listings, etc. In some embodiments, thecontent server 317 may include software to validate (or initiate thevalidation of) user identities and entitlements, locate and retrieve (orinitiate the locating and retrieval of) requested content, encrypt thecontent, and initiate delivery (e.g., streaming, transmitting via aseries of content fragments) of the content to the requesting userand/or device.

The system may also include one or more off-net devices 318. As notedabove, an off-net device 318 may be similar to the gateway 311, but canbe a device connected to a third party network that may be part of adifferent network from the one of the termination system 310. Forexample, if the termination system 310 is a land-based fiber opticand/or coaxial cable network, the off-net device 318 may be a wirelesscellular or satellite network. Aside from the fact that the off-netdevice 318 may be part of a different network from the on-net devices(e.g., gateway 311), the off-net device 318 may behave in a similarmanner as described herein for the gateway 311.

FIG. 4 illustrates an example signaling flow diagram for setting up amulticast server 307's multicast feed. The multicast server 307 may beconfigured to continuously transmit a plurality of multicast streams(e.g., IP multicast streams) to groups of devices that have subscribedto or joined the multicast streams. The FIG. 4 signaling flow mayillustrate one example of how such a stream is established.

In step 401, the multicast controller can determine that a particularpiece of content should be multicast, and configure that new piece ofcontent for use in the multicast feed. Determining whether a piece ofcontent should be multicast may depend on a variety of factors tomaximize efficient use of the multicast server 307. In some embodiments,the multicast controller 308 (or other device in the network) maymonitor actual or anticipated demand for the various items of content inthe system (movies, shows, sporting events, television networks, etc.),and use the multicast signal to carry popular content.

In some embodiments, this ranking can take into account differentversions of content as well. So, for example, if the high definitionversion of a popular movie is expected to be highly demanded, but thestandard definition version is not, then the ranking can list the highdefinition version higher than the standard definition one. As anotherexample, the versions can differ based on the end device (CPE) beingused to consume the content. If there are a large number of deviceshaving a first configuration (e.g., a large number of mobile telephoneshaving 4-inch touch displays), then the version of content fitting thatdevice can be ranked higher than versions of the content that areconfigured for other devices (e.g., mobile telephones having smallerdisplays, or non-touch displays).

In some embodiments, the ranking can be time-based. For example, thecontroller 308 can define a time interval (e.g., 2 weeks), and canrevisit the ranking of content versions periodically according to thetime interval.

In some embodiments, the ranking can take into account geography aswell. For example, the controller 308 can gather statistical informationfor the geographic area served by a given termination system 310, andrestrict its ranking based on information for that area (e.g., the typesof CPEs in that area, the movies that are popular in that area in viewof viewer demographics, etc.). If a large number of homes in a givenarea, e.g., a single ZIP code, happen to have a particular type of CPE(e.g., a brand of mobile television device is popular in that area),then the version of a movie configured for that type of CPE may beranked higher than versions of the movie set for other devices.

The configuration of the content may include, for example, preparingmultiple versions of a piece of content, such as a highdefinition/resolution version, a standard definition version, differentencodings and/or file formats of the same content (e.g., the sametelevision program can be encoded with different video encoderprotocols).

This configuration can also include generating a map identifying whichtermination system servers 310 are used with which multicast servers307. The various termination systems 310 can be dispersedgeographically, each servicing a range of premises and gateways 311, andeach termination system can be associated with (or include) a multicastserver 307 that is configured to handle multicast streams for the usersserviced by its corresponding termination system 310.

In step 402, the multicast controller 308 may transmit a multicast setuprequest to a multicast server 307. This message may be in the form of anHTTP POST message, and the message body may include a variety ofparameters. For example, the message may include a Multicast IDparameter, which is a unique identifier for a particular piece ofcontent.

The message may include a Content Path parameter, which can be anaddress, such as an IP address or URL, where a piece of content may befound.

The message may include Content Manifest File Name. A content's manifestfile may include metadata information to help a multicast server 307interpret the content file's various profiles. As noted above, eachpiece of content may be available in a variety of different versions.For example, a movie might be available in a high definition version, astandard definition version, versions having different compressionratios, different encryption types, different required bitrates, etc.Each of those versions may have a profile, identifying a file locationfor that version, its necessary bitrate, encoder/decoder, resolution,etc., and the manifest file may inform the multicast server 307 as tothe formatting of the content's profile. This can be especially useful,for example, where multiple different parties supply different content,and each party uses its own unique formatting for providing profileinformation.

The manifest file may identify a plurality of profile levels, each levelidentifying an encryption, compression, or resolution level that issuitable for delivery given a predetermined bitrate. For example, thefile may identify two different profile levels, one for high bitrate useand one for low bitrate use, and these levels may identify differenttypes of compression suitable for the available bitrates (e.g., a lowbitrate level could use a more lossy level of encryption because thecontent files would be smaller).

The message may include a List of Profile Levels parameter, which canspecify the profiles in the manifest file that the multicast servershould deliver. For example, the multicast controller may determine thata particular multicast server should offer 3 versions of a particularvideo program: one high bitrate version, one medium, and one low bitrateversion. The List of Profile Levels parameter may identify these threeprofile levels to the multicast server. In some embodiments, thisparameter is optional, and when the parameter is absent, the multicastserver can be automatically configured to deliver the highest bitrateprofile contained in the manifest file.

The message may include a Server Multicast Source parameter and a Listof Server Multicast Groups parameter. These parameters may identify, foreach profile, a corresponding multicast source (e.g., an address of themulticast server 307) and group (e.g., name of a multicast group).

In response to the setup message 402, the multicast server 307 canacknowledge the request by sending a response 403, and then proceed toprepare a multicast stream for the content. This can begin by sending arequest for the manifest file in step 404. The request can be an HTTPGET request, and although FIG. 4 illustrates the request being sent tothe delivery network 305, the request can be addressed to any desiredlocation on the network 305, for example, at a content delivery network(e.g., using an address identified by the Content Manifest File Nameparameter discussed above). For example, the manifest file may belocated at a content server responsible for the content, such as aserver associated with one of the encoders 301/302 discussed above. Therequest may also identify the manifest file name being requested.

In response, in step 405, the manifest file source may supply themanifest file to the multicast server 307. In step 406, the multicastserver may compare parameters, such as the List of Profile Levelsparameter, with the available profiles in the manifest file, and selectone or more profiles for the one or more versions of the content thatthe multicast server will make available to users.

Then, in step 407, the multicast server 307 can issue a request to thecontent source (represented in FIG. 4 as part of the content deliverynetwork 305) for the one or more versions of the content. The requestcan be another HTTP GET message, and can identify network addressparameters for the content source, identify the content itself, andidentify the one or more requested profiles. If the content is afragmented portion of a larger piece of content (e.g., a six-minuteportion of a television program), the request in step 407 may identifythe segment of the program and, if the program is divided into evensmaller fragments, then the request can also identify the specificfragment or all of the segments.

In step 408, the content source supplies the requested content, and instep 409, the multicast server can generate one or more multicaststreams (e.g., IP multicast streams) carrying the content. Thegeneration and use of these streams is discussed further below.

The FIG. 4 signal flow resulted in the multicast server 307 obtainingdesired content and making that content available in a variety ofmulticast feeds. FIG. 5 illustrates a signaling flow for maintaining andmonitoring those multicast feeds by the multicast server 307. Forexample, steps 501-504 illustrate communication sequences to allow amulticast controller 308 and multicast server 307 to remainsynchronized, for example, in terms of the groups and profiles that theserver 307 is serving. In step 501, the multicast controller 308 canissue a multicast list request to the multicast server 307. This requestcan be an HTTP GET request, and can include a Multicast Identifier,identifying a desired multicast list (e.g., a listing of multicaststreams that the controller is expecting the server 307 to besupplying).

In step 502, the multicast server 307 can respond with a list of themulticast streams that it is currently offering. The response caninclude, for example, an ID identifying the multicast stream in theresponse, a Content Path parameter identifying the content itself (e.g.,its name, the address of its source, etc.), and a List of Profile Levelsparameter listing the profile levels for the content being offered bythe multicast server. The response can also include a Server MulticastSource identifying the multicast server 307, and a List of ServerMulticast Groups parameter, identifying the one or more multicast groupsthat contain each profile version of the content. For example, a givenversion of content may have a single profile, but that version may beoffered in multiple multicast groups, so the List of Server MulticastGroups parameter may list those groups.

In step 503, the multicast server 307 may transmit a multicast feedrequest message to the multicast controller 308. The request may beanother HTTP GET message, and may identify the server itself, as well asa Multicast ID listing the multicast streams that the server 307 iscurrently transmitting.

In response, in step 504, the multicast controller 308 may transmit aresponse containing a Response Code identifying the type of response(success, failure, etc.), and a List of Multicast Info parameter, whichcan contain information for one or more multicast groups. The responsecan identify, for example, the Multicast ID, the Content Path of thecontent source, the List of Profile Levels for the content that themulticast server 307 is to provide, the Server Multicast Source, and alisting of the Multicast Groups that the multicast server 307 is tosupport. As noted above, each profile may be associated with multiplemulticast groups, so this listing (one per profile) can identify thosegroups.

Steps 505-508 illustrate a communication sequence that allows themulticast server 307 and controller 308 to exchange status informationfor the various multicast streams being offered by the server 307. Instep 505, the multicast controller 308 can issue a multicast statusrequest to the multicast server 307. The request can be an HTTP GETrequest, and can include a Multicast ID parameter, identifying one ormore multicast streams that the multicast controller 308 wishes tomonitor.

In step 506, the multicast server 307 can respond, for example, with aResponse Code identifying the success/failure of the request, and a Listof Multicast Status value containing information for the one or morerequested multicast streams identified in the controller 308's request.This list can identify the Status of a particular multicast stream, suchas whether it is active, as well as a Content Bit Rate parameteridentifying the bit rate at which the particular content is beingdelivered in this stream.

Steps 505-506 were initiated by the multicast controller 308. As analternative, the multicast server 307 can voluntarily report its statusinformation to the controller 308. Steps 507-508 illustrate this, inwhich the server 307 can transmit (step 507) its status information asan HTTP POST request, and the controller 308 can respond (step 508) witha Response Code to indicate a successful (or failed) delivery of thestatus information.

FIG. 6 illustrates an example signal flow for stopping or tearing down amulticast feed when it is no longer desired or needed. First, in step601, the multicast controller 308 may determine that a particularcontent item in an existing multicast feed being sent by the multicastserver, or the feed itself, no longer needs to be included. This canoccur for a variety of reasons. For example, the multicast controller308 may determine that the number of users who are subscribed orotherwise joined to a particular multicast group has fallen below apredetermined threshold to justify the multicast feed, and that the fewremaining users who wish to watch content in the feed would be betterserved with unicast transmissions instead. For example, the controller308 may maintain a count of the number of devices that are members ofthe multicast group for a particular piece of content, and if thatmembership count falls below a predetermined level (e.g. less than 1000member devices). In some embodiments, the controller 308 may maintain ademand listing for each available piece of content in the system, andonly the top 100 pieces of content (based on number of requests, demand,anticipated demand, etc.) can be sent as multicasts (the other contentwould be sent as unicast streams upon demand as needed).

In step 602, the multicast controller 308 can send a teardown multicastrequest to the multicast server 307. This request can be an HTTP POSTrequest, and can contain, for example, a Multicast ID parameter,identifying the multicast feed that is to be terminated. The request canalso include a Reason Code parameter, identifying to the multicastserver the reason(s) or the teardown. In response, the multicast server307 can terminate the feed, release resources reserved for the feed, andsend a response in step 603 confirming the teardown. The response cancontain a Response Code, indicating that the teardown was successful (orif it failed).

The flows in FIGS. 4-6 have discussed an example of how a multicast feedcan be established, monitored and terminated by the multicast server 307and its controller 308. FIGS. 7-9 will illustrate an example of how auser can discover the existence of the available multicast feeds and usethem. FIG. 7 illustrates an example of multicast discovery, in which theuser's device, such as gateway device 311, can learn the existence ofavailable multicast feeds.

In step 701, the multicast server 307 can be transmitting one or moremulticast feeds (and may continuously do so). These feeds may be IPmulticast data streams supplied to one or more termination systems 310supported by the server 307. Those streams can contain items of contentthat have been packaged by the packager 303, for example, and convertedto an IP stream. The termination system 310 can use this multicaststream to supply a multicast stream to the various gateways 311 usingany desired multicast protocol. For example, the termination system 310can use a PacketCable Multimedia (PCMM) multicast or Internet GroupMulticast Protocol (IGMP). In such a stream, an RF portion of a cablenetwork can be used as a multicast datastream to deliver data tosubscribing modems on the network.

In step 702, the multicast controller 308 can transmit a multicastlineup message to a user's home or premises gateway 311 (or in someembodiments, to a termination system 310 serving the gateway 311). Thistransmission can occur periodically (e.g., daily, every 15 minutes,etc.), or on demand as needed. The lineup message can include a listingof the various multicast streams being supplied in the step 701multicast transmission. The listing can include, for example, a ContentPath parameter (identifying a network address where a piece of contentin the stream can be found), and a Profile Name parameter identifying amanifest file profile for the content (as noted above, the profiles mayidentify characteristics of a version of the content, such as itsbitrate, resolution, etc.). The list can include a Server MulticastSource parameter, providing a unique identifier for the multicast server307 offering the listed multicast stream, and a Server Multicast Groupparameter, providing a name for the listed multicast stream.

The lineup supplied to the gateway 311 can be filtered based on avariety of factors. For example, the controller 308 may have previouslyreceived configuration information from the gateway 311 identifying theCPE device(s) that are registered with and/or served by the gateway 311.Before sending the lineup in step 702, the controller 308 can edit thelineup to remove entries for content versions that are incompatible withthe gateway 311's CPEs (e.g., versions that require larger screens thatare in use at the home, or require decoding/decrypting functionality notpresent in the gateway 311 or its CPEs, etc.). The controller 308 may beaware of the digital rights management capabilities of the various CPEs,and can remove listings for content to which the CPE would not be ableto gain access.

The filtering can also remove content that is undesired by the users ofthe gateway 311. For example, users may inform the gateway 311 (whichcan inform the controller 308) that the users do not wish to viewavailable content of a certain genre (e.g., sports, adult programs,children's cartoons, etc.), or that certain programs are undesired.

Although the lineup transmission is illustrated once here, thetransmission can actually occur periodically. For example, the lineupcan be sent every night at a given time. Or, the lineup can be sentpiecemeal, such as sending the overall lineup once a day, and sendingincremental updates to the lineup more frequently (e.g., every 30minutes). The incremental updates may simply indicate what changes haveoccurred to the lineup since the last update.

In step 703, the gateway 311 may send a confirmation, indicating thatthe lineup message was received (or containing a Response Codeidentifying whether it was received, or if a failure occurred).

As discussed, steps 702/703 may involve the multicast controller 308sending a notification to the gateway 311 of the multicast lineup (e.g.,listing of multicast streams or groups) that the termination system 310is supplying. In preparing this list, the multicast controller 308 canconsult a stored database mapping the gateway 311 to termination systems310, to identify the particular termination system 310 that services thegateway 311. The controller 308 can also filter the list of multicaststreams to omit streams that are unusable by the gateway 311 or itssupported devices (e.g., CPEs behind the gateway). For example, thecontroller 308 may have previously received a registration listing ofthe various devices supported by the gateway 311, along with informationidentifying the devices' characteristics (e.g., their processingcapacity, available memory, encryption and digital rights managementinformation, display resolution and size, bandwidth and bitrate, etc.).

Alternatively, or in addition, the gateway 311 can request transmissionof the lineup. This can occur, for example, periodically according to aschedule (e.g., once a day), or on demand when a new device signs onwith the gateway 311 or when an existing device indicates a change incapability (e.g., addition or removal of application program, physicalmemory, etc.). Step 704 includes an example multicast lineup request,which can be an HTTP GET request sent from the gateway 311 to themulticast controller 308. The request itself may include a DeviceIdentifier parameter, identifying the gateway 311 and/or a device beingserviced by the gateway, indicating that the identified device isrequesting the multicast lineup.

In step 705, the gateway controller 308 can assemble the multicast listinformation, as in step 702. In doing so, the controller 308 can use theDevice ID to consult one or more device profiles, to identify multicaststreams that are compatible with the requesting device (e.g., displayresolution, processing capacity, encryption, etc.).

In step 706, a device (e.g., CPE) serviced by the gateway 311 may send arequest directly or via the gateway 311 to a session manager 309,requesting access to a stream or item of content. For example, thedevice may have previously downloaded a listing of available contentfrom an Internet site, and the user of the device may have clicked on alisted piece of content. In step 706, the request may be a message tothe session manager 309, identifying the CPE device and the requestedcontent.

In step 707, the session manger 309 may establish a session for the user(e.g., authenticate that the user is permitted to access the content,determine which version to provide, process payment, etc.), and mayrespond by supplying the CPE device with an address for the requestedcontent (e.g., a Universal Resource Locator address for a version of thecontent that the device can handle).

In step 708, the CPE device can send a request to the gateway 311,requesting that the gateway 311 establish a session, such as a unicastsession, to receive the content desired by the CPE user. The request mayidentify the address supplied by the session manager 309.

In step 709, the gateway 311 may determine whether to honor the CPEdevice's request for a unicast session. In doing so, the gateway 311 mayfirst determine whether the requested content is currently beingmulticast by the multicast server 307. To do so, the gateway 311 mayconsult a stored copy of the multicast list obtained in steps 703 or705, and compare it with the profile information for the contentrequested by the CPE device. If the requested version of the requestedcontent is already being multicast by the multicast server 307, thegateway 311 can proceed to the FIG. 8 method/signaling flow (discussedbelow), and join the multicast group. If the requested version of therequested content is not being multicast, then the gateway 311 canproceed with setting up the requested unicast session using the suppliedcontent address. Although the process of FIG. 7 has been described usingcommunications through a gateway 311, all communications may occurdirectly between CPE device 312 and controller 308 or manager 309.

FIG. 8 illustrates an example signal flow for establishing a multicastoperation, such as a cache fill operation, when one or more of theavailable multicast streams has been requested by a device supported bythe gateway 311. In step 801, the gateway 311 may transmit a cache fillsetup request to the multicast controller 308. The setup request may bean HTTP POST request message, and may include a Device ID parameteridentifying the gateway 311 (or CPE device) requesting the cache fill, aContent Path parameter identifying the address of the desired content, aProfile Name identifying the profile version of the content to becached, a Server Multicast Source identifying the multicast server 307,and a Server Multicast Group identifier identifying a multicast groupcontaining the requested content.

In step 802, the multicast controller 308 can transmit a cache fillsetup request to the session manager 309. The setup request may be anHTTP POST request message, and may include a Device IP Address for thedesired content, a Content Path identifying the location of the contentat that address, the Server Multicast Source and Group values in theprior request 801, and additional bitrate information. The bitrateinformation may identify the average and/or maximum bitrate that therequesting device can receive and/or process (the controller 308 canpossess this information in advance through querying or measurement ofthe device and/or reporting by the device).

In step 803, the session manager 309 can respond with a message,indicating whether the prior message was successfully received, andwhether the cache fill setup is successful.

The multicast controller may, in turn, transmit a response 804 back tothe home gateway 311. The steps 801-804 cache setup signaling may beomitted, for example, if the multicast session protocol permitsmulticast session joining without involving the session manager 309.

In step 805, the gateway 311 may transmit a session join message to thetermination system 310. That message, which can be an Internet GroupManagement Protocol (IGMP) Join message, can identify the MulticastServer Source and Group to be joined. IGMP may be used to supportmulticast transmission between the termination system 310 and a gateway311. Additionally, the multicast session from the multicast server 307to the termination system may follow a different standard, such as thePacketCable Multimedia (PCMM) standard.

The termination system 310 can, in turn at step 806, transmit a servermulticast join message to the multicast server 307, identifying the sameMulticast Server Source and Group. In steps 807-808, the multicastserver 307 can begin to transmit the multicast content to thetermination system 310, which in turn transmits it to the gateway 311.The gateway 311 (or other CPE serviced by it) can then begin to receive,transmit and/or store the multicast content for consumption by a user.The gateway 311 can also simply forward the received multicast stream tothe CPE device, but identify the content as being the requested unicaststream that the device requested in step 708. So, for example, thegateway 311 can respond to the device's request (e.g., its request for aunicast stream of the requested content) by supplying a multicast streamin step 809, and yet still identify the multicast stream as a unicaststream.

In some embodiments, the multicast controller 308 may use a periodicmessage (e.g., a heartbeat message) to confirm or monitor that therequesting device is still using the requesting multicast. For example,if no heartbeat message is received from the requesting device (or itsgateway 311) for a predetermined amount of time (e.g., 5 minutes), themulticast controller 308 can automatically terminate a multicast session(or decrement a group member count by one to remove the requestingdevice from the membership list, which may result in termination of themulticast session if there are insufficient remaining subscribers tojustify the group).

The heartbeat message may include an HTTP POST request message from thegateway 311 to the controller 308, as illustrated in step 810. Theheartbeat message can identify the gateway 311 (Device ID), and can alsocontain a list of the active cache fill operations that the gateway 311is receiving and using. The list can identify the Content Path, ProfileName, Server Multicast Source and Server Multicast Group parametersdiscussed above, to identify those multicast streams that are in use.The gateway 311 can maintain an internal timer, and automaticallytransmit the heartbeat at the required intervals.

In step 811, the controller 308 can transmit a response to the gateway311, confirming that the heartbeat was received.

FIG. 9 illustrates an example teardown sequence when a gateway 311determines that it no longer needs to receive or subscribe to aparticular multicast session (e.g., if the requesting device is turnedoff, or if the user changes channels to view different content). In step901, the gateway 311 may determine that the stream is no longer needed.

In step 902, the gateway can transmit a multicast leave message to thetermination system 310, and in step 903 the termination system can senda corresponding multicast leave message to the multicast server 307.These messages can identify the Server Multicast Source and Groupparameters discussed above, identifying a particular multicast streamthat is no longer needed by the gateway 311. In response, thetermination system 310 and multicast server 307 may remove the gateway311 from the list of addressees in the specified multicast stream(s).

In some embodiments, the session manager 309 may monitor the membershipof the various multicast feeds for content, and in step 904, the gateway311 may transmit a cache teardown request to the multicast controller308. The message may be a POST Request message, and may contain similarparameters as the cache fill setup message 801. The multicast controller308 may then transmit a cache teardown request message to the sessionmanager 309 (containing similar parameters as the cache setup message802), and subsequent corresponding responses can be sent from thesession manager 309 in step 906 and the multicast controller 308 in step907, reporting back the results of the teardown request.

The signaling flow diagrams discussed above illustrate example processesthat can occur for supplying multicast content. FIG. 10 illustrates analternative view of those processes and signals, to help illustrate anexample logical flow. The FIG. 10 example process can begin when a userof a CPE device (e.g., a display device, a computer, a set-top box, amobile device, etc.) decides to access content. This can occur, forexample, when a user views an electronic program guide listing ofavailable video programs, and chooses one to watch. In step 1001, theuser's CPE may transmit a request to the CPE's gateway 311, indicatingthe desire for a unicast session to watch the selected program. This canuse, for example, the signaling of step 708 discussed above.

In response, the gateway 311 may determine, in step 1002, whether therequested content is available as a multicast signal from a multicastserver 307 serving the gateway 311. The requested content here maysimply be data or a video program, but it can be a specific version ofthe data or program as well (e.g., coded using a particular encoder,encrypted in a particular encryption, having a predetermined resolution(e.g., high definition, standard definition, etc.), having predetermineddigital rights management parameters, sized for a predetermined average(or minimum or maximum) transmission bitrate, etc.). To make thisdetermination, the gateway 311 may consult a stored copy of themulticast listing received in steps 702 or 705.

If the desired version of the desired content is available as amulticast stream, then the gateway 311 can proceed to step 1003, andjoin the multicast group session by using, for example, the signaling ofFIG. 8. Additionally, the gateway 311 can begin to cache the content asit is received, storing it in a memory, such as a temporary portion ofRAM 203.

In step 1004, the gateway 311 can transmit the received content to therequesting CPE. In doing so, the gateway 311 can package the content asif it were the same unicast-type session requested in step 1001.Accordingly, the CPE may be indifferent, and unaware, of the fact thatthe gateway 311 has used a multicast session to obtain the content inthe unicast request.

In step 1005, the gateway 311 can determine if there are more portionsof the requested content to follow. As noted above, a piece of contentmay be fragmented and subdivided for treatment as distinct portions. A30-minute television program may be divided into six separate files,each containing five minutes of the program. In the step 1005determination, the gateway may determine whether the next portion of theprogram is desired. If it is, then the process can return to step 1002to retrieve the next portion of the program.

If it is not (e.g., if the user has changed channels away from theoriginally requested content, or if the original program has ended),then the gateway can proceed to step 1006, and determine if the groupjoin should be cached. In other words, the gateway 311 can determinewhether it should remain a member of the multicast group carrying theoriginally-requested content. To make this determination, the gateway311 can consult any of a number of predefined parameters. For example,the gateway 311 can be configured to remain a member of a group for apredetermined period of time (e.g., 5 minutes) after the user changeschannels. By doing so, the gateway 311 can quickly receive the contentagain should the user return to the original channel, skipping some ofthe initial signaling used in step 1003 to first join the group, andallowing for a faster channel change.

Another example parameter may be based on the user's preferences. A usercan designate certain programs, services, or channels as favorites, andthe gateway 311 can cache a group join involving those programs,services, or channels for a longer period of time than for otherprograms, services, or channels.

Note that in the cache join of step 1006, the underlying content itselfneed not be cached when the user is no longer watching the originallyrequested program. Instead, the cache join 1006 may simply retain thefact that the gateway 311 has joined the group.

If a cache join is desired, then in step 1007, the gateway 311 mayremain a member of the originally-requested group. Going forward, whilethe user is not watching the program in this multicast group, thegateway need not actually store the incoming multicast packets of thatgroup, but the gateway can simply retain membership in the group. Insome embodiments, remaining a member of the group in step 1007 need notinvolve any additional processing at all—the gateway 311 may simply donothing to leave the group, and/or send periodic heartbeat messages tokeep its membership in the group active.

If a cache join is not desired, then in step 1008, the gateway 311 cantake steps to leave the group. This can involve, for example, thesignaling of FIG. 9.

Back in step 1002, a determination was made if requested content wasavailable as a multicast. If it was not available, then in step 1009,the gateway 311 can determine whether a similar version of the contentis available as a multicast. A similar version may be the sameunderlying content title (e.g., the same movie, television show, etc.),but having different characteristics from that requested. For example, amulticast group may exist carrying a version of the movie, but at adifferent bitrate from the desired bitrate; or using a differentencoding algorithm from that originally requested; or at a differentscreen resolution or size from that requested.

If a similar version of the requested content is available, then thegateway may, in step 1010, offer a hint, query, or suggestion to therequesting CPE device regarding the similar content version. This hintmay simply be a message to the CPE indicating that the requested contentis available in a different version from that originally requested, andmay identify the relevant difference from the original request. The CPEmay process this and determine whether the other (alternate) version isacceptable. For example, it may be acceptable if the CPE happens to havethe correct decoder, bandwidth, display resolution, etc. to accommodatethe different version. The CPE can also display a prompt to the user,asking if a slightly different resolution/bitrate/etc. version would beacceptable. The gateway 311 may then receive (at step 1011) anindication from the CPE as to whether the alternate version isacceptable.

If the alternate is acceptable, then the gateway 311 can proceed to step1003, and join the multicast group carrying that alternate version. Ifthe alternate is not acceptable, then in step 1012, the gateway canproceed with establishing a unicast session for the content, inaccordance with the original request. The gateway 1012 can alsoestablish this unicast session if, in step 1009, a similar version ofthe requested content was not available as a multicast.

In the discussion above, the gateway 311 may determine in step 1005 thatmore content is desired (e.g., more fragments of the requested programare going to be sent or are available in the multicast), and return tostep 1002. In doing so, the gateway 311 may retain knowledge of thepreviously joined multicast group, and immediately proceed to step 1003(to receive the next portion the multicast). Alternatively, the gateway311 can conduct a new determination of the availability of the contentas a multicast. This new determination may be useful, for example,should the original multicast experience an error (e.g., a missedpacket), or be torn down due to lack of membership numbers. In thatsituation, what was once available might no longer be available, and thegateway 311 can establish a unicast session (at step 1012) instead. So,the gateway 311 can convert from a multicast to a unicast session duringthe course of a program, and the CPE need not even be aware of anychange.

Using some of the above described features, quality of service terms canbe enforced at the termination system 310 for multicast streams. Forexample, if the termination system 310 determines that the availablebandwidth leading to the gateway 311 (and other gateways serviced by thetermination system) is running low, the termination system can furtherreduce the number of unicast streams in the system by increasing thenumber of multicast streams, and forcing users and CPE devices to acceptsimilar alternatives identified in step 1009. The termination system canalso lower the bitrate of the various multicast streams, and causefuture requests for higher bitrate versions to be diverted to the lowerbitrate similar versions instead.

FIG. 11 illustrates an example process in which a consumption devicerequests content. In step 1101, a consumption device (e.g., CPE 312 a)may issue a request for content to its corresponding gateway 311. Therequest may be entered, for example, by a user who views an electronicprogram guide on the CPE 312 a, and makes a selection therefrom.

In step 1102, the gateway 311 may send a request for the content to thetermination system 310, which may be a DOCSIS cable modem terminationsystem (CMTS). Alternatively, as discussed above, the CPE maycommunicate directly with the termination system 310 or servers 308/309.The request itself may be sent, for example, using a multicast protocolmessage, such as PacketCable Multimedia (PCMM) from Cablelabs orInternet Group Management Protocol (IGMP) from the IETF (InternetEngineering Task Force). The message may include a source identifierfield and a group identifier field, which can normally identify a sourceaddress of multicast content and a group identifier identifying themulticast group (the group identifier can be resolved during routinginto a group of destination addresses for eventual unicast delivery tothe members of the multicast group). However, in some embodiments, thegroup identifier can be used for a different purpose. In someembodiments, the group identifier can identify a bitrate value for therequesting device (e.g., the requesting consumption device or CPE). Thebitrate value can identify, for example, the average, minimum, and/ormaximum bitrate that the consuming device can receive via its connectionto the gateway 311, or the bitrate needed to support the requestedcontent. For example, the requested content can be a variable bitrate(VBR) content.

In step 1103, the TS 310 can determine if the requested content isalready being transmitted by the TS on any of its downstream channels,such as a downstream logical channel. If the content is not alreadybeing sent, the TS 310 may use the group identifier value from therequest to determine the bitrate capacity (or demand) of the requestingconsuming device CPE in step 1104.

In step 1105, the TS can determine if it has sufficient capacity toinitiate a new logical downstream transmission carrying the requestedcontent at the requested bitrate. If it has capacity, the TS can proceedto step 1106, and establish a new logical connection to the gateway 311.The logical connection can be any desired type of communicationconnection, such as a secure session.

In step 1107, the TS can obtain the requested content from its source.Obtaining this content can be done in any desired manner, such as usinga PIM (Protocol Independent Multimedia) session.

In step 1108, the TS may announce the logical connection to the gateway311. This can include, for example, informing the gateway of theaddress, encryption, encoding, bitrate, channel location, and any otherinformation to inform the TS of how to locate, receive, decrypt anddecode the content to be sent in the logical connection.

In step 1109, the TS may begin to transmit the requested content on thelogical channel it created, and in step 1110 the gateway can receive thecontent and process it for delivery to the requesting consumption deviceCPE. After the requesting device ceases to consume the content (e.g., ifthe user changes channels, or turns the device off), the TS can beinformed of this by the gateway 311, and the TS can tear down thelogical connection. In some embodiments, the TS can wait for apredetermined amount of time to pass before tearing down the connection,in case the device (or another device) returns to the content.Alternatively, a session may be torn down if its bandwidth is needed fora higher priority content.

Returning to step 1103, the TS may determine that it is already sendingthe requested content. For example, this may occur the second time agateway issues a request for content that's already been received andprocessed by the TS as discussed above. If the TS is already sending therequested content, then the TS can skip to step 1108, and announce thelogical connection to the gateway.

Returning to step 1105, the TS may determine that it does not have thecapacity to support the requested bitrate for the requested content. Inthat event, the TS can proceed to step 1111, and deny the requestedconnection, sending a response to the requesting gateway and consumptiondevice. The denial may cause the requesting device to issue a newrequest for a lower bitrate version of the content.

Aspects of the disclosure have been described in terms of illustrativeembodiments thereof. While illustrative systems and methods as describedherein embodying various aspects of the present disclosure are shown, itwill be understood by those skilled in the art, that the disclosure isnot limited to these embodiments. Modifications may be made by thoseskilled in the art, particularly in light of the foregoing teachings.

As an example, the same on-net consumption device can become an off-netconsumption device if, for example, the device leaves a range of thegateway 311, and instead begins using a third party network to requestthe same content. For example, a cell phone can use an IEEE 802.11 wi-ficonnection to receive content while a user is at home, and can insteaduse a cellular telephone connection to request and receive the samecontent while away from home. In both instances, the requesting cellphone can transmit its request, in the same format, to the samemulticast controller 308 or session manager 309.

As another example, each of the features of the aforementionedillustrative examples may be utilized alone or in combination orsubcombination with elements of the other examples. For example, any ofthe above described systems and methods or parts thereof may be combinedwith the other methods and systems or parts thereof described above. Forexample, one of ordinary skill in the art will appreciate that the stepsillustrated in the illustrative figures may be performed in other thanthe recited order, and that one or more steps illustrated may beoptional in accordance with aspects of the disclosure. It will also beappreciated and understood that modifications may be made withoutdeparting from the true spirit and scope of the present disclosure. Thedescription is thus to be regarded as illustrative instead ofrestrictive on the present disclosure.

What is claimed is:
 1. A method, comprising: receiving, by a gateway device, a multicast listing identifying content items available for multicast reception; receiving a content request from a consumption device, the content request being a request to establish a unicast session to obtain requested content; determining that the requested content is listed in the multicast listing; joining a multicast group identified in the multicast listing; supplying the requested content from the multicast group to the consumption device in response to the consumption device's content request; receiving a content request for a second item of content from the consumption device; determining that a requested version of the second item of content is not listed in the multicast listing; determining that a similar version of the second item of content is listed in the multicast listing; transmitting a message to the consumption device, informing the consumption device that the similar version is available; and receiving approval from the consumption device to supply the similar version of the second item of content instead of the requested version of the second item of content.
 2. The method of claim 1, further comprising: while supplying the requested content to the consumption device, the gateway device switching from the multicast group to a unicast transmission for the requested content without further input from the consumption device, and without informing the consumption device of the switching.
 3. The method of claim 1, further comprising: the gateway device remaining a member of the multicast group after determining that the consumption device no longer needs the requested content.
 4. The method of claim 3, wherein if the consumption device does not resume consumption of the requested content within a predetermined period of time, the gateway device leaves the multicast group.
 5. The method of claim 4, further comprising storing parameters identifying different lengths of time to be used as the predetermined period of time for different programs or services.
 6. The method of claim 3, further comprising, after determining that the consumption device no longer needs the requested content, remaining a member of the multicast group for an amount of time that depends on a user preference corresponding to the requested content or a service offering the requested content.
 7. The method of claim 3, further comprising the gateway device remaining a member of the multicast group of the requested content and storing portions of the requested content received while the consumption device needs the requested content, and after the consumption device no longer needs the requested content, remaining a member of the multicast group without storing portions of the requested content received while the consumption device no longer needs the requested content.
 8. A method, comprising: receiving, at a gateway device, a multicast listing identifying content items available for multicast reception; receiving a unicast content request from a consumption device, the unicast content request being a request to establish a unicast session to obtain content; determining that the requested content is listed in the multicast listing; subscribing to a multicast group identified in the multicast listing; supplying the requested content from the multicast group to the consumption device in response to the consumption device's unicast content request; and conducting a cache join of the multicast group upon the consuming device ceasing to access the requested content in the multicast group, wherein the cache join includes remaining a member of the multicast group without caching content from the multicast group.
 9. The method of claim 8, further comprising: while supplying the requested content to the consumption device, switching from the multicast group to a unicast transmission for the content without further input from the consumption device, and without informing the consumption device of the switching.
 10. The method of claim 8, further comprising: receiving a unicast content request for a second item of content from the consumption device; determining that a requested version of the second item of content is not listed in the multicast listing; determining that a similar version of the second item of content is listed in the multicast listing; transmitting a message to the consumption device, informing the consumption device that the similar version is available; and receiving approval from the consumption device to supply the similar version of the second item of content instead of the requested version of the second item of content.
 11. The method claim 10, further comprising selecting the similar version based on available bandwidth between the computing device and a termination system.
 12. The method of claim 8, further comprising: remaining a member of the multicast group after determining that the consumption device no longer needs the requested content.
 13. The method of claim 12, further comprising: leaving the multicast group if the consumption device does not resume consumption of the requested content within a predetermined period of time.
 14. The method of claim 8, further comprising managing bandwidth usage by adjusting multicast sessions.
 15. A method, comprising: receiving, by a gateway device, a multicast listing identifying content items available for multicast reception; receiving a content request from a consumption device, the content request being a request to establish a unicast session to obtain requested content; determining that the requested content is listed in the multicast listing; joining a multicast group identified in the multicast listing; supplying the requested content from the multicast group to the consumption device in response to the consumption device's content request; and the gateway device remaining a member of the multicast group after determining that the consumption device no longer needs the requested content.
 16. The method of claim 15, further comprising: while supplying the requested content to the consumption device, switching from a multicast group to a unicast transmission for the content without further input from the consumption device, and without informing the consumption device of the switching.
 17. The method of claim 15, further comprising: receiving a content request for a second item of content from the consumption device; determining that a requested version of the second item of content is not listed in the multicast listing; determining that a similar version of the second item of content is listed in the multicast listing; transmitting a message to the consumption device, informing the consumption device that the similar version is available; and receiving approval from the consumption device to supply the similar version of the second item of content instead of the requested version of the second item of content.
 18. The method of claim 15, further comprising: leaving the multicast group if the consumption device does not resume consumption of the requested content within a predetermined period of time.
 19. The method of claim 18, wherein the predetermined period of time is a user-configured parameter. 